A. The Prior Art
The art is replete with various types of data entry devices wherein digital data in the form of electronic signals may be manually generated by the actuation of various types of data input keyboards including such keyboards employing thumb wheels, dials, a plurality of toggle switches, latching type key switches arranged in groups and interlocked such that only one keyswitch within a group may be activated at any one time, and arrays of momentary actuation pushbuttons in which the sequence that the individual buttons are actuated is also significant.
Typically, such keyboards have character indicia permanently associated with each of the key positions indicating the value of or meaning associated with the actuation of that particular key.
Accordingly, a bystander in the vicinity of such a prior art keyboard upon witnessing which keys were actuated (and if significant in what sequence) could then examine the keyboard itself to determine the actual value of the data that the user had just input, and the security of the data would thereby be compromised.
If the user was inputting secret or confidential information (such as a secret identification code known only to himself used to establish his identity to an electronic bank teller or other electronic device), then a possible security expedient would be to shield the keyboard with a privacy screen such that the fingers of the user operating the keyboard were hidden from view. However, if such a privacy shield were to be effective, it would also at least partially obscure the view of the user himself of the indicia associated with the various keys and could thus result in erroneous data being entered and/or the user being seriously inconvenienced. Such a shield would also add bulk and weight to the keyboard that would be undesirable in a self-contained portable application such as an electronic credit card verification system.
Such limitations of the prior art were in part addressed in U.S. Pat. No. 3,587,051 which discloses a device wherein the user responds to the random illumination of combinations of lights, each of the different lights being permanently marked with a different digit. The user would take each random pattern of illuminated and non-illuminated lights to generate mentally a data encoding key which he then would mentally apply to his secret combination to generate a derived code which he then would input to the device by actuating the appropriate switch or switches. Upon his successfully repeating such an encoding process for a predetermined number of different randomly generated patterns, the apparatus would be able to determine whether or not the user was in possession of the correct secret combination. Although such a prior art system might find utility in certain applications involving a limited number of sophisticated, highly trained users, it would not appear to be adaptable for use by the general public on an everyday basis.